Wastewater treatment process including irradiation of primary solids

Abstract

The present invention provides a method for treating wastewater in which the majority of solids and biological oxygen demand compounds are separated from the wastewater feed using a primary separation process, to produce a solids phase and a water phase. The solids phase is irradiated to reduce the level of pathogens such that it is safe to use as a soil substitute and/or additive so that the solids can thus be disposed of in an environmentally-friendly manner. In additional embodiments, the solids that have been disinfected by radiation are mixed with a suitable inert filler material to produce a soil substitute, fertilizer, compost, or other soil additive. The liquid phase is treated in a substantially smaller system than would be required for treating the full-strength wastewater that can include a suspended media biological regeneration reactor system. The liquid treatment system can include a high flux adsorbent material treatment system integrated with a low flux adsorbent material biological regeneration reactor.

The invention claimed is: 
     
       1. A method for treating wastewater that contains solids and biological oxygen demand compounds, the process comprising:
 separating a majority of the solids and biological oxygen demand compounds from the wastewater feed using a primary separation process to provide a solids phase and a water phase including wastewater, the solids phase containing an initial level of pathogens; 
 irradiating the solids phase to reduce the level of pathogens; 
 mixing the wastewater with adsorbent material in a mixing zone for a time sufficient for adsorption of contaminants from the wastewater onto the adsorbent material; 
 separating and removing a major portion of the wastewater from the mixture of wastewater and adsorbent material; 
 passing the adsorbent material having contaminants adsorbed thereon and a minor portion of the wastewater to a biological regeneration reactor; 
 retaining the adsorbent material and wastewater in suspension in the biological regeneration reactor for a period of time that is sufficient to allow microorganisms in the biological regeneration reactor to biologically act on at least a portion of the adsorbed contaminants; 
 discharging biologically treated water effluent from the biological regeneration reactor; and 
 recycling regenerated adsorbent material to the mixing zone. 
 
     
     
       2. The method of  claim 1 , further comprising homogenizing the separated solids phase prior to the irradiation. 
     
     
       3. The method of  claim 1 , wherein the irradiating comprises exposing the solids to one or more of beta-ray, gamma-ray, x-ray or electron beam radiation. 
     
     
       4. The method of  claim 1 , wherein the step of separating the solids and biological oxygen demand compounds from the wastewater feed produces low concentration wastewater. 
     
     
       5. The method of  claim 1 , further comprising removing solids from the biological regeneration reactor water effluent using a membrane operating system, a clarifier and/or a settler. 
     
     
       6. The method of  claim 1 , which further comprises shearing any accumulated biomass from the adsorbent material prior to recycling to the mixing zone. 
     
     
       7. The method of  claim 6 , further comprising separating the biomass from the adsorbent material prior to recycling the adsorbent material to the mixing zone. 
     
     
       8. The method of  claim 1 , further comprising mixing the irradiated solids phase with a filler material to produce a soil, compost, or fertilizer product.